How to Exclude from Yahoo/MSN results!

I want to exclude underconstruction site

[fm101]

I want to know fastest way to exclude under-construction site from yahoo and MSN results (google haven't index it yet), at start I haven't put robots.txt and yahoo/msn indexed it and it have #1-#3 positions for targeted keywords and start getting traffic, but I don't want to show my site till its fully developed.
does
User-agent: *
Disallow: /

will work fine to exclude it from yahoo/msn results?

thanks for your help.

[submitx]

If your site is already included and you use robots.txt, it will take a while before it is removed. You will have to wait until the spider it again, which may take 1-4 weeks or more. However, you can also use a javascript to detect the referal and then redirect the visitors somewhere else, but that doesn't solve the problem I guess.